<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <title>在线尝试 Bootstrap 实例</title>
    <meta name="viewport" content="width=device-width,
                                     initial-scale=1.0,
                                     maximum-scale=1.0,
                                     user-scalable=no">

    <link rel="stylesheet" href="css/bootstrap.css">
    <script src="js/jquery-3.2.1.js"></script>
    <script src="js/bootstrap.js"></script>
</head>
<body>
<div class="container">

    <div class="row">
        <div class="col-sm-6 col-md-3">
            <a href="#" class="thumbnail">
                <img src="images/2.jpeg"
                     alt="通用的占位符缩略图">
            </a>
        </div>
        <div class="col-sm-6 col-md-3">
            <a href="#" class="thumbnail">
                <img src="images/2.jpeg"
                     alt="通用的占位符缩略图">
            </a>
        </div>
        <div class="col-sm-6 col-md-3">
            <a href="#" class="thumbnail">
                <img src="images/2.jpeg"
                     alt="通用的占位符缩略图">
            </a>
        </div>
        <div class="col-sm-6 col-md-3">
            <a href="#" class="thumbnail">
                <img src="images/2.jpeg"
                     alt="通用的占位符缩略图">
            </a>
        </div>
    </div>

</div>
</body>
</html>